I guess the "biometric identification linked to a payment instrument" issue is mostly trust.

Do I trust the entity that identify me using biometrics ?

Do I trust it with my biometric data ?

If I link a payment method, do I trust it with access to my payment details ?

With Amazon Go at WF, I was fine to let Amazon know and store my hand biometrics, and I was fine enough with Amazon know what I purchase at WF, as long as I had something back (loyalty program).

Scaling this though would negatively impact the trust. Maybe I do not want Amazon to know "everything" I purchase everywhere (even though Visa/MC/Amex already know it...)